Preparation of oil soluble sulfonic acids useful as dispersant additives

ABSTRACT

A SULFONIC ACID COMPOSITION IS PREPARED BY SEPARATELY SULFONATING (A) AN ALKYLATE COMPOSITION CONSISTING ESSENTIALLY OF ONE OR MORE MONOALKARYL COMPOUNDS IN WHICH THE ALKYL SUBSTITUENT CONTAINS FROM ABOUT 20 TO 40 CARBON ATOMS, AND (B) AN ALKYLATE COMPOSITON CONTAINING FROM ABOUT 5 WEIGHT PERCENT TO ABOUT 35 WEIGHT PERCENT DIPHENYLALKANES, FROM ABOUT 5 WEIGHT PERCENT TO ABOUT 50 WEIGHT PERCENT ALKYLATED TETRALINS, AND FROM ABOUT 25 WEIGHT PERCENT TO ABOUT 75 WEIGHT PERCENT DIALKYHLBENZENES, AND HAVING AN AVERAGE MOLECULAR WEIGHT OF FROM ABOUT 300 TO ABOUT 500. THE SULFONIC ACID REACTION MIXTURES DERIVED FROM THE TWO ALKYLATES ARE THEN SEPARATELY GRAVITY SETTLED AND A PRIMARY ACID-SLUDGE SPLIT IS TAKEN TO REMOVE THE SLUDGE FROM EACH REACTION MIXTURE. THE DE-SLUDGED CRUDE SULFONIC ACIDS FROM THE TWO ALKYLATES ARE THEN MIXED AND DISSOLVED IN HEXANE. THE HEXANE SOLUTION OF THE MIXED SULFONIC ACIDS IS THEN PERMITTED TO SETTLE AND ANOTHER ACID-SLUDGE SPLIT IS MADE TO REMOVE THE SLUDGE. THE FIRST ALKYLATE STARTING MATERIAL MAY BE A SO-CALLED DIMER ALKYLATE PREPARED BY ALKYLATING BENZENE WITH A DIMERIZED TETRAMER OF PROPYLENE, AND THE SECOND ALKYLATE STARTING MATERIAL MAY BE A BOTTOMS FRACTION YIELDED IN THE FRACTIONATION OF AN ALKYLATE MIXTURE PRODUCED BY ALKYLATING BENZENE WITH NORMAL CHLOROPARAFFINS CONTAINING 8 TO 18 CARBON ATOMS.

United States Patent US. Cl. 252353 20 Claims ABSTRACT OF THE DISCLOSUREA sulfonic acid composition is prepared by separately sulfonating (a) analkylate composition consisting essentially of one or more monoalkarylcompounds in which the alkyl substituent contains from about 20 to about40 carbon atoms, and (b) an alkylate composition containing from aboutweight percent to about 35 weight percent diphenylalkanes, from about 5weight percent to about 50 weight percent alkylated tetralins, and fromabout 25 weight percent to about 75 weight percent dialkylbenzenes, andhaving an average molecular weight of from about 300 to about 500. Thesulfonic acid reaction mixtures derived from the two alkylates are thenseparately gravity settled and a primary acid-sludge split is taken toremove the sludge from each reaction mixture. The de-sludged crudesulfonic acids from the two alkylates are then mixed and dissolved inhexane. The hexane solution of the mixed sulfonic acids is thenpermitted to settle and another acid-sludge split is made to remove thesludge. The first alkylate starting material may be a so-called dimeralkylate prepared by alkylating benzene with a dimerized tetramer ofpropylene, and the second alkylate starting material may be a bottomsfraction yielded in the fractionation of an alkylate mixture produced byalkylating benzene with normal chloroparaffins containing 8 to 18 carbonatoms.

BACKGROUND OF THE INVENTION (1) Field of the invention This inventionrelates to the preparation of oil soluble sulfonic acids suitable foruse as dispersant additives to lubricating oils, and more particularly,to such sulfonic acids as are particularly suited for neutralization andoverbasing in-situ in a non-volatile carrier material.

(2) Brief description of the prior art It is Well known that certainrelatively high molecular weight sulfonates constitute valuabledispersants when added to lubricating oils. These sulfonates are oftenused to suspend or peptize small particles of basic metal compounds inthe lubricating oil to which the sulfonates having the metal compoundsdispersed therein are added, and in this manner, function to permit analkaline reserve to be imparted to the lubricating oil so that harmfulacidic products of fuel combustion and lubricating oil oxidation can beneutralized.

The oil soluble sulfonates described are prepared by sulfonating varioustypes of alkylate starting materials. One widely used type of alkylatestarting material which is an excellent sulfonation feedstock is aso-called dimer alkylate which is a mixture of monoalkaryl compounds inwhich monoalkylbenzene compounds containing from 20 to 40 carbon atomsin highly branched alkyl substituents predominate. Dimer alkylates ofthis type are prepared by alkylating benzene with a dimerized tetramerof propylene. The method of preparing the dimer used in alkylation iswell understood in the art.

Another alkylate material which has been employed as Patented Nov. 21,1972 a sulfonation feedstock is a bottoms fraction yielded in thefractionation of an alkylate mixture produced by alkylating benzene withnormal chloroparafiin compounds containing from 8 to 18 carbon atoms.The overhead derived from the fractionation is sulfonated to yieldvaluable biodegradable detergents. The bottoms fraction can besulfonated to prepare oil soluble sulfonic acids of the type underdiscussion. This bottoms fraction, in general, contains from about 5weight percent to about 35 weight percent diphenylalkanes, from about 5weight percent to about 50 weight percent alkylated tetralins, and fromabout 25 weight percent to about weight percent dialkylbenzenes. Thealkyl substituents of the alkylated compounds in the bottoms fractioncontain from about 10 to 18 carbon atoms, and the average molecularweight of the bottoms fraction is from about 300 to about 500. For useas a sulfonation feedstock, the bottoms alkylates which contain arelatively high proportion of dialkylbenzenes have been normallypreferred, and frequently the raw bottoms alkylate remaining afterremoval of the lighter detergent grade alkylate is topped or furthertreated to increase the concentration of dialkylbenzenes therein, and tolower the quantity of diphenylalkanes contained therein. The lattermaterials do not sulfonate well and tend to decrease the overall qualityof the sulfonate product.

In cases where the raw bottoms alkylate is not further topped to removethe diphenylalkanes to increase the concentration of thedialkylbenzenes, the raw bottoms alkylate may contain residual smallamounts of the higher boiling portion of the biodegradable detergentalkylate stock. This material is thus included in the described rangesof amounts of dialkylbenzenes and alkylated tetralins. The process ofthis invention is particularly useful in employing bottoms alkylatematerial containing relatively high concentrations of diphenylalkanes.

For economic reasons, as well as to improve certain properties in thefinal sulfonic acid compositions, it has become a practice in thelubricating oil additive art to prepare a blend or mixture of thedescribed dimer alkylate and bottoms alkylate, then co-sulfonate themixture, followed by removal of spent acid sludge, and finallypurification of the final sulfonic acid product. Certain productspecifications for sulfonate type lubricating oils have been easily metby sulfonate mixtures prepared in this way, but others have beenmarginally met, and it has been recently found that certain variances inthe processes of producing the two alkylates and co-sulfonating themixed alkylates yield sulfonate products which do not meet allspecifications; particularly a color specification imposed by theindustry.

BRIEF DESCRIPTION OF THE PRESENT INVENTION The process of the presentinvention provides a method by which improved sulfonates for use aslubricating oil dispersant additives, can be prepared from dimeralkylate and bottoms alkylate starting materials. The procedureconstitutes an improvement with respect to co-sulfonation proceduresheretofore in use in which the two alkylates described are initiallymixed or blended, and then sulfonation is carried out on such mixture,followed by sludge removal and purification. The process of the presentinvention results in an upgrading of the sulfonic acids yielded in thata higher ratio of actual sulfonic acid to other acidic products ispresent, the sulfonic acids produced have a higher combining weight, andno significant sacrifice in yield of sulfonic acids per unit of alkylatecharged is sufiered. Moreover, the sulfonic acids produced by theprocess of the invention can be neutralized and overbased to produce anoverbased sulfonate additive which is improved over those prepared bythe co-sulfonation process previously employed in that the overbasedsulfonates are characterized in having a lower viscosity and improvedcolor.

Broadly described, the process of the present invention comprisesinitially carrying out separate sulfonations of (a) an alkylatecomposition which consists predominantly of one or more monoalkarylcompounds in which the alkyl substituent contains from about 20 to about40 carbon atoms, and (b) a second alkylate composition which containsfrom about weight percent to about 35 weight percent diphenylalkanes,from about 5 weight percent to about 50 weight percent alkylatedtetralins, and from about 25 weight percent to about 75 weight percentdialkylbenzenes. Preferably, the second alkylate subjected to theprocess of the invention contains between about 40 weight percent and 75weight percent dialkylbenzenes and less than about 20 weight percentdiphenylalkanes. After carrying out the separate sulfonations of the twodescribed alkylates, a primary sludge split is taken on each of the tworeaction products. The sludge split is obtained by permitting thereaction mixture to gravity settle over an extended period of time, andthen removing the spent acid sludge from the crude sulfonic acid. Afterremoving the sludge from each of the sulfonation mixtures, the desludgedcrude sulfonic acids are then mixed and are dissolved in a light organicsolvent boiling below about 150 C. and preferably between about 40 C.and 120 C. Suitable materials include petroleum naphtha and lightparaffins, such as hexane, heptane and octane. The solution of the mixedsulfonic acids is then permitted to settle, and another acid-sludgesplit is made to remove the sludge which has settled out. The finalsolution of mixed sulfonic acids is then preferably purified bytechniques well understood in the art.

It is an important object of the present invention to provide a processfor preparing a mixture of sulfonic acids which is suitable forpreparing overbased sulfonate additives which may be used to impartreserve alkalinity and high dispersancy to lubricating oils.

A more specific object of the invention is to improve the sulfonic acidand sulfonate products derived from dimer alkylate, and from alkylatesanalagous to the bottoms alkylate produced in the manufacture ofdetergent grade alkylate by alkylating aromatic materials withchlorinated paraffin compounds.

Other objects and advantages of the invention will become apparent asthe following detailed description of certain preferred embodiments ofthe invention are considered in conjunction with the accompanyingdrawings which illustrate certain aspects of the invention and certainbenefits derived therefrom.

BRIEF RESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustratingthe manner in which the process of the present invention is practiced.

FIG. 2 is a bar graph comparison of the properties of various sulfonicacid and overbased sulfonate products derived from the process of thepresent invention with the same products as prepared by co-sulfonationof mixed alkylates as heretofore practiced.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTIONFIG. 1 of the drawings may be referred to as an aid in understanding theprocess of the present invention as it is hereinafter described. Sincethe two types of alkylates which are separately sulfonated in theprocess are typified by the dimer alkylate and bottoms alkylate to behereinafter more specifically described, these are indicated in the FIG.1 diagram.

As previously indicated, the process of the present invention iscommenced by separately sulfonating two types of alkylate materials. Oneof these contains at least 70 weight percent, and preferably at least 80weight percent, monoalkaryl compounds in which an aryl compound issubstituted by a single alkyl substituent containing from about 20 toabout 40 carbon atoms. A typical alkylate of this type is sometimesreferred to in the art as dimer alkylate, and is made by alkylatingbenzene with a highly branched dimerized propylene tetramer containingfrom about 20 to about 40 carbon atoms. The lakylate is derived from thepropylene refinery stream by processes will understood and widelypracticed in the art, and is characterized in having an averagemolecular weight of from about 350 to about 600. The dimer alkylate maycontain up to 25 weight percent of dialkylbenzenes which constitute themajor constituent other than the described monoalkaryl compounds.

An alkylate, other than dimer alkylate, fitting the general definitionof the first of the two alkylates sulfonated in the process of thisinvention is an alkylate in which the monoalkaryl compounds are alkylsubstituted benzene compounds in which the alkyl substituents aresubstantially straight chain in character and contain from about 20 toabout 40 carbon atoms. Such alkyl benzenes can be prepared by alkylatingbenzene with a substantially straight chain olefin, such as an a-olefin.

In sulfonating the first alkylate of the type described, the alkylate isusually initially diluted with a light mineral oil, such as 100 S.S.U.viscosity pale oil, and is then sulfonated by conventional sulfonationprocedures. Although $0 or mixtures of S0 and 80;, may be used tosulfonate the alkylate, 20% oleum is preferably employed to sulfonatethe alkylates, whereby sulfonic acids substantially free of sulfurdioxide and sulfuric acid are yielded. The oleum is added slowly to theoil-diluted alkylate to a weight ratio of from about 1.0:1 to about1.6:1 oleum to alkylate, while holding the temperature below about 80 C.and preferably below about 60 C. After addition of the oleum, thereaction mass is post-stirred for a period of from about 20 minutes toabout 40 minutes at a temperature of from about 40 C. to about 80 C. andpreferably from about 55 C. to about '60" C. The reaction mixture isthen transferred to a separatory device, such as a separatory funnel,and is settled for from about 8 to about 16 hours at a temperature ofabout 50 C. The sludge phase is then removed.

The second alkylate which is subjected to separate sulfo nation containsfrom about 5 weight percent to about 35 weight percent diphenylalkanes,and preferably from about 5 weight percent to about 20 weight percent.The alkylate further contains from about 5 weight percent to about 50weight percent alkylated tetralins, and from about 25 weight percent toabout weight percent di-n-alkylbenzenes. The average molecular weight ofthis alkylate is from about 300 to about 500. As has been indicated, atypical alkylate of this type is that which is derived by afractionation process in which the total alkylate prepared by reactinglong chain chlorinated n-paratfin hydrocarbons with aromatic compounds,and particularly benzene, is subjected to fractional distillation. Thebottoms portion (as contrasted with the overhead) which is yielded bysuch fractionation is an alkylate coming within the definition anddescription of the second alkylate subjected to sulfonation in theprocess of the present invention. This bottoms alkylate will typicallycontain from about 40 weight percent to about 75 weight percentdi-n-alkylbenzenes in which the alkyl substituents contain from about 8to 18 carbon atoms and are bonded to the benzene group through asecondary carbon atom of the alkyl chain, from about 10 to about 25percent diphenylalkanes, from about 5 weight percent to about 18 weightpercent tetralins, of which the majority are alkylated tetralins, andfrom about 4 weight percent to about 12 weight percent naphthalenes andindanes. Of the di-n-alkylbenzenes constituting the major constituent ofthe bottoms alkylate, from about 50 weight percent to about weightpercent of these are para-disubstituted alkylbenzenes, and the balanceare meta-disubstituted alkylbenzenes. Typically, the bottoms alkylate isseparated from the overhead, which overhead constitutes an alkylatevaluable for the production of biodegradable detergents, byfractionating the alkylate mixture to a cut point of 160 C. at mm. Hg.If it is desired to reduce the diphenylalkane content of the bottomsalkylate thus recovered to the preferred level of from about 5 weightpercent to about 20 weight percent, further distillation can be carriedout. The average molecular weight of the bottoms alkylate may range fromabout 300 to about 500.

As contrasted with the sulfonation of the first alkylate material ashereinbefore described, the second alkylate, of which the bottomsalkylate specifically identified is an example, is preferably sulfonatedneat; that is, it is preferred that no dilution with a light mineral oilbe effected prior to sulfonation. In carrying out the sulfonation, thealkylate is stirred, and 20% oleum is slowly added to the alkylate in aweight ratio of from about 1.3:1 to about 1.9:1 while maintaining thetemperature of the reaction mixture below about 80 C. and preferablybelow about 60 C. After the oleum has been added, stirring is continuedfor a period of from about 20 minutes to about 40 minutes thereafterwhile maintaining the temperature at from about 40 C. to about 80 C.,and preferably from about 55 C. to about 60 C. After this time a lighthydrocarbon solvent boiling between about 40 and 150' C., and preferablybelow about 120 C., is added in an amount suflicient to provide about0.5 to 3.0 weight parts of the solvent per weight part of the alkylatecharged. Suitable solvents include light petroleum naphthas, hexane,heptane, octane, and mixtures thereof. As an alternative, up to 30weight percent of the light hydrocarbon solvent can be replaced by adiluent oil such as pale oil. The mixture is then stirred for anadditional period of from about to about 30 minutes at refluxtemperature, which is generally from about 55 C. to 60 C.

After this time, the crude sulfonation mass is transferred to aseparatory device, such as a separatory funnel, and is permitted tosettle for a period of from about 8 hours to about 16 hours at ambienttemperature. A primary sludge split to remove the spent sulfuric acidsludge is then taken, and the hexane-sulfonic acid phase is recovered.

As has been previously indicated herein, a practice in use prior to thepresent invention has been to initially mix or blend the two alkylatesof the types described, and then perform a co-sulfonation of the mixedalkylates, followed by sludge separation. The mixed sulfonic acidproduct yielded by such co-sulfonation procedure has, however,occasionally failed to meet certain specifications, particularly thecolor specification, when certain slight variations in the alkylateproduction process which are diflicult to control are encountered. Wehave determined that separate sulfonation, followed by separate sludgeremoval from the sulfonic acid products produced by the separatesulfonations, then followed by combining of the sulfonic acids, followedfinally by a secondary sludge split, results in the production of animproved mixed sulfonic acid product. This procedure is schematicallyillustrated in FIG. 1. Although the reason for the improvement inresults is not thoroughly understood, it is believed that the tetralinsin the second alkylate, of which bottoms alkylate of the type describedis typical, tend to solubilize certain undesirable sulfonatablematerials, specifically the diphenylalkanes in this alkylate, when theco-sulfonation procedure is followed. In other words, the mixed sulfonicacids produced upon co-sulfonation tend, due to the solubilizing effectof the tetralins in the mixed alkylate starting material, to includecertain undesirable materials which detract from the quality of thefinal mixed sulfonic acid product. Where the sulfonations are carriedout separately, it is believed that the primary sludge split taken uponthe crude sulfonic acid product of the bottoms alkylate sulfonationefiectively removes certain undesirable by-products from the sulfonicacid product at this point (these being removed in the sludge), and theresult is that these materials which cause the final product to be offspecification when co-sulfonation is utilized, have been removed, andthe final mixed sulfonic acid product is of higher quality.

As indicated in FIG. 1, after the primary sludge split has beenaccomplished in the primary settlers to remove spent sulfuric acidsludge from the crude sulfonic acids, the crude sulfonic acids aremixed, diluted with a paraffinic hydrocarbon, such as hexane, and placedin a secondary settling device, such as a separatory funnel. Thedilution with light hydrocarbon solvent is carried out to adjust thesulfonic acid concentration to about 0.4 to about 0.8 milli-equivalentof acid per gram of the diluted mixture. In general, from about 0.20 toabout 2.0 volume of hexane is utilized per volume of crude acids. Thediluted mixed sulfonic acids are permitted to gravity settle for aperiod of from about 8 to about 16 hours, and the sludge is thenremoved.

It should be here pointed out that, in lieu of gravity settling ashereinbefore described, de-sludging of the two separately sulfonatedalkyates to achieve the primary sludge split can be accomplished bycentrifugation, as can the secondary sludge split accomplished after thecrude sulfonic acids from the two alkylates have been combined.Centrifugation is particularly amenable to usage in desludging thesulfonic acid product resulting from sulfonation of the bottoms alkylatematerial.

After the crude sulfonic acids have been recovered from the final sludgeremoval step, the acids are purified by initially de-gassing the acidsby blowing an inert gas, such as nitrogen, through the acids for about15 minutes. Calcium hydroxide, in an amount equivalent to about 1.5times the amount needed to neutralize the sulfuric acid, is then addedto the crude acids, and the mixture is again degassed using an inert gasto blow the mixture for a period of about 45 minutes while heating themixture to a temperature of from about 30 C. to 35 C. The solution isthen filtered, and the sulfonic acids thus prepared and purified can beused in the preparation of overbased sulfonate compositions suitable foruse as additives to lubricating oils.

The following examples typify the practice of the invention, and alsoprovide illustrations of the manner in which mixed alkylateco-sulfonation has been previously utilized in the production of oilsoluble sulfonic acids. It will be understood that other alkylatesdiffering to some extent in constitution from those specifically citedin the examples may be used as starting materials, and some variation inprocess conditions may be tolerated without diffculty.

EXAMPLE 1 575 grams of a dimer alkylate which contained 81.8 molepercent monoalkylbenzenes (each containing from about 22 to about 38carbon atoms in the highly branched alkyl substitutents), 13.6 molepercent para-dialkylbenzenc compounds, and 4.6 mole percentmeta-dialkylbenzene compounds, and having a molecular weight, asdetermined by osmometer, of 362, were charged, along with 345 grams ofpale oil having a viscosity of S.S.U. at 210 C. to a creased flask, andmechanical agitation was commenced. 20% oleum was charged to the flaskover a period of 20 minutes. The exothermic reaction was maintained at atemperature of between 55 C. and 60 C. during the addition of the oleum.After addition of the oleum, the reaction mass was post-stirred for aperiod of 30 minutes, and was then charged to a separatary funnel andpermitted to gravity settle overnight at 50 C. On the following day,sludge split was taken to remove sludge from the crude sulfonic acid-oilmixture. 1,070 grams of the crude acid-oil product were recovered, and624.4 grams of sludge were removed.

In another sulfonation run, alkylate bottoms recovered from a detergentalkylate process of the type hereinbefore described was the sulfonationcharge stock. This alkylate was characterized in containing, asdetermined by mass spectrometer, 40.7 volume percent alkylbenzenecompounds containing from 8 to 18 carbon atoms in the alkylsubstituents, 24.9 volume percent diphenylalkanes, and 23.3% tetralins.The average molecular weight of the alkylate was 350. 1,500 grams of thealkylate were charged to a creased reaction flask and were mechanicalagitated as 20% oleum was added to the flask over a period of minutes.During this time, the temperature of the reaction mixture was maintainedbelow 60 C. After addition of the oleum, the mixture was post-stirredfor a period of minutes. Following the post-stirring, 2,250 ml. ofhexane was added to the reaction mixture, and mechanical mixing was thencontinued for a period of 15 minutes at a temperature of between 55 C.and 60 C. The mixture was then charged to a separatory funnel andpermitted to settle at ambient temperature overnight. On the followingday, a sludge split was taken. 2,768 grams of crude acidhexane solutionwere recovered, and 2,923 grams of sludge were removed.

All of the crude acid-oil product from the described sulfonation of thedimer alkylate was combined and mixed with 1,100 grams of the crudeacid-hexane solution derived from the described bottoms alkylenesulfonation. The combined sulfonic acid products were mechanicallymixed, and 2,790 ml. of additional hexane were added during the mixing.The hexane-acid mixture was then charged to a separatory funnel andpermitted to gravity settle at ambient temperature overnight. On thefollowing day, a secondary sludge split was taken, and there wereisolated 3,833 grams of sulfonic acid solution. 166.3 grams of sludgewere separated.

EXAMPLE 2 A dimer alkylate of the type described in Example 1 wasdiluted with a pale oil having a viscosity of 100 S.S.U. at 210 C. in aweight ratio of 0.54:1 diluent oil to alkylate. 20% oleum was thenslowly added to the mixture in an amount suflicient to give a weightratio of oleum to alkylate of 1.2: 1. The sulfonation conditions weresimilar to those described in Example 1 in the part thereof which refersto the sulfonation of the dimer alkylate. Following sulfonation, aprimary sludge split was taken after permitting the reaction mixture tosettle overnight in a separatory funnel.

In another sulfonation, a bottoms alkylate having a molecular weight asdetermined by osmometer of 344 and containing, by mass spectrometeranalysis, 40.6 volume percent alkyl benzene, 35.7 volume percentdiphenylalkanes, and 16.7 volume percent tetralins was sulfonated with20% oleum in a weight ratio of oleum to alkylate of 1.9: l. The alkylatewas sulfonated neat, and the temperature and time conditions weresimilar to those used in the sulfonation of bottoms alkylate asdescribed in Example 1. Upon completion of the post-stirring utilized inthe sulfonation, hexane was added to the reaction mixture in an amountequal to the amount of alkylate used in the sulfonation. The reactionmixture was then charged to a separatory funnel and permitted to gravitysettle overnight. After gravity settling, a primary sludge split wastaken to recover the crude acid-hexane solution from the spent acidsludge.

The acid-hexane solution thus produced was then combined with the crudeacid-oil product produced by the akylation of the dimer alkylate asdescribed earlier in this example. The sulfonic acids were mixed in a1:1 weight ratio. After combining the acid products in the mannerdescribed, hexane was added to the combined crude acids in a volumeratio of 1.2:1 hexane to crude 8 acid (the term crude acid herereferring to the crude acid, hexane and oil present in the combinedcrude acid products of the two sulfonations). The hexane-acid mixturewas then permitted to gravity settle for a period of about 15 hours, anda secondary sludge split was taken to remove sludge from the acid-hexanemixture.

EXAMPLE 3 Dimer alkylate of the type utilized in Example 1 wassulfonated neat, using a weight ratio of 20% oleum to alkylate of 12:].Upon completion of the post-stirring period of the sulfonation, a volumeof hexane was added to the reaction mixture in a weight ratio of 1:1hexane to starting alkylate. The crude sulfonic acid product wasrecovered by a primary sludge split after settling overnight.

2,000 grams of the bottoms alkylate utilized in Example 2 were chargedto a creased sulfonation flask equipped with a mechanical stirrer,thermometer and dropping funnel. 20% oleum in a weight ratio of 1.9:1oleum to alkylate was added to the alkylate and sulfonation of thebottoms alkylate carried out as described in Example 2. Hexane was thenadded to the reaction mixture in an amount equal to the amount ofalkylate sulfonated. After overnight settling, a primary sludge splitwas then taken to recover the crude hexane-acid solution.

The crude sulfonic acid-hexane product produced from the bottomsalkylate was then combined with the crude sulfonic acid-hexane productproduced by alkylation of the dimer alkylate described earlier in thisexample in a sulfonic acids weight ratio of 1:1. The mixed acids werethen diluted with about 1.2 volumes of hexane, and a secondary sludgesplit was taken after permitting the mixture to stand overnight.

EXAMPLE 4 500 grams of the dimer alkylate described in Example 1 weremixed with 655 grams of pale oil and 500 grams of the bottoms alkylatedescribed in that example, and the mixture was then charged to a creasedflask and sulfonated with 1,900 grams of 20% oleum in the mannerdescribed in Example 1 as being utilized for the sulfonation of dimeralkylate. After completion of the post-stirring period, the sulfonationmass was charged to a separatory funnel and gravity settled at 50 C.overnight. On the following day, a sludge split was taken and 1,758grams of sludge were removed to leave 1,731 grams of the crude acid-oilproduct. To 1,196 grams of crude acid-oil produced in the mannerdescribed were added 1,880 m]. of hexane. After homogenization by handmixing in a separatory funnel, the mixture was permitted to gravitysettle overnight at ambient temperature. On the following day, asecondary sludge split was taken, and there were isolated 2,357 grams ofhexane-sulfonic acid solution. 98.2 grams of secondary sludge wasremoved.

EXAMPLE 5 A mixed alkylate charge stock which contained 60 weightpercent of the bottoms alkylate and 40 weight percent of the dimeralkylate described in Example 2 was employed in a cosulfonation run. 100S.S.U. viscosity pale oil was used as a diluent in a weight ratio of 0.5:1 diluent to total alkylate charge stock. The oil diluted alkylate wasthen subjected to sulfonation using 25% oleum in a weight ratio of 1.9:1oleum to total alkylate charge. At the end of the post-stirring period,the crude sulfonic acid-oil mixture was transferred to a separatoryfunnel, and after a suitable period of gravity settling, a primarysludge split was taken. Hexane was then added to the crude acid-oilraffinate recovered from the sludge split in a volumetric ratio of 1.5:1hexane to acid-oil product. A secondary sludge split was then taken.

9 EXAMPLE 6 For the purpose of further examining the co-sulfonation ofmixed alkylates, the bottoms alkylate and dimer alkylate described inExample 3 were mixed in a 60:40 weight ratio. The mixed alkylates werethen sulfonated in the manner described in Example 1 for the sulfonationof the dimer alkylate, but utilizing a weight ratio of 20% oleum toalkylate charge of 1.6:1 and without pale oil dilution. Upon completionof the alkylation, a weight of normal hexane equivalent to the weight ofalkylate charge was added to the reaction mixture, and the hexanediluted mixture was then permitted to stand overnight at 50 C. A primarysludge split was taken on the following day to remove the sludge fromthe mixture. There was then charged to the crude acid-hexane mixture, anadditional volume of hexane equivalent to the volume of the crudeacid-hexane mixture remaining after the primary sludge split. Thismixture was then permitted to gravity settle overnight, and a secondarysludge split was taken to isolate the crude acid-hexane mixture from thespent acid sludge materials.

EXAMPLE 7 For the purpose of evaluating the crude hexane-sulfonic acidproducts produced by co-sulfonation and by separate sulfonations asdescribed in Examples 1-6, certain analyses and tests of the severalproducts were made, and the results compared. The results obtained aretabumixture was again de-gassed with nitrogen for an additional periodof 45 minutes while heating the mixture to a temperature of from C. toC. The solutions were then filtered, and the flask and funnel used infiltering rinsed with hexane to recover all of the sulfonic acid.

The purified sulfonic acid products were then utilized to prepareoverbased barium and calcium sulfonate dispersions. For the purpose ofpreparing the overbased barium sulfonate dispersions, the sulfonic acidcharge was calculated so as to yield an overbased product having anacetic acid base number of approximately 70, and to contain about 46.5weight percent neutral barium sulfonate. Thus, in each instance, 200grams of the purified sulfonic acid-hexane solution were charged to al-liter creased flask equipped with a mechanical stirrer, thermometerand heating mantle. A neutral mineral oil having a viscosity of 100S.S.U. at 210 C. was then added to adjust the activity of the sulfonicacid solution as necessary to make the 46.5 percent active product.

Methanolic barium oxide solution was then added slowly from a droppingfunnel over a period of about 10 minutes to neutralize the sulfonic acidand to provide excess barium oxide. Carbon dioxide was then blownthrough the mixture from a sintered glass tube at a rate of about 250ml./min. until the reaction mass became acidic to anaphthol benzeneindicator (the time required was from about 15 to about 20 minutes). Thesolvents were then distilled overhead to a pot temperature of 150 C.,and the product stripped with carbon dioxide for a period of lated inTable I. 30 15 minutes.

TABLE I Example Number Co- Co- Co- Sep- Sep- Sepsuliosultosuito- Typesuliouatlonarate arate crate nation nation nation Crude hexane sultonicacid:

Total acid, meqJg. 0. 802 1. 183 0. 78B 1. 034 1. 170 Sulionic acid,meq./ 0. 582 0. 638 0. 573 0. 623 0. 669 Acid ratio 1 3 9-3 4. 2 7. 6 8.6 Na sulfonatlon ASTM (D color 2. 6 1. 6 4. 0 2. 5 2. 5 Yield data.-

Cornbining Wei ht, (RSOH) 5B 39 444 450 429 Grams RSO H g., alkylatecharge 0- 8B 0- 82 0. 81 0. 87 0. 83 0. 8s

1 Expressed as weight percent sulfuric acid based on total Weight ofsulfonic acid present. I Determined by ASIM D1500-67T modified bydissolvin 7.0 grams of sodium sulfonate in ml. of hexane. Determined bycolumn analysis of the corresponding so ium sulfonate prepared from thefinal hexane diluted sulfonic acid.

It will be noted in referring to Table I that the crude hexane-sulfonicacid products produced by separately sulfonating the two alkylate typesdescribed were characterized in having higher combining weights andbetter A.S.T.M. sodium sulfonate color than the products derived fromthe co-sulfonation processes. Two of the sulfonic acid products hadlower acid ratio values than their counterpart products produced byco-sulfonation.

EXAMPLE 8 The crude sulfonic acid products produced in Examples 1-6 werepurified by placing the product to be purified TABLE II Example NumberType sulionation Sep- Sep- Sep- Co-sulfo- Co-sulfo- Clo-sulfoarete aratearate nation nation nation b r 76 68 71 69 70 71 l g r e d geti ve a-47- 2 46- 5 46- 5 46. 4 46.3 46. 5 Viscosit 210 F., SSU. 302. 2 219. 3293. 7 332.0 237. 8 335. 0 ASTM din. color 1 3. 5 a0 3. 0 5. 0 3. 5 a. 5

1 Determined by ABTM Dl500-57T modified by dissolving 7.6 grams of theoverbased barium sulfonate dispersion in 50 ml. hexane.

in a creased three-necked flask equipped with a mechanical stirrer,thermometer and heating mantle. The crude sulfonic acid was thende-gassed for a period of 15 minutes by blowing with nitrogen through asintered glass tube at ambient temperature. Calcium hydroxide in anamount 1.5 times the weight needed to neutralize the sulfuric acid wasthen added, and after the addition, the 75 tion in many cases, wasreduced significantly in compari- 11 son to the color ratingcharacteristic of the dispersions derived from the cosulfonationprocedure.

In order for the data reproduced in Tables I and II to be moremeaningfully compared, runs carried out with related starting materialsand in substantially the same manner, except for the difference ofco-sulfonation, as contrasted with separate sulfonation, are compared inside-by-side relation in bar graph form in FIG. 2 of the drawings. Thus,in Example 1, the dimer alkylate was sulfonated in 100 pale oil and inExample 4, the mixed alkylates were co-sulfonated in such oil. Moreover,in these two runs, the bottoms alkylate and dimer alkylates used werethe same materials. In Examples 2 and 5, the processing conditions weresimilar in that in Example 2, the dimer alkylate was sulfonated in oil,and in Example 5, the alklate mixture was sulfonated in oil. Moreover,the bottoms alkylate and dimer alkylate used in both these runs wereidentical, although the bottoms alkylate differed from that used inExamples 1 and 4. In Examples 3 and 6, the sulfonation of all alkylateswas carried out neat, with post-hexane addition in each case.

In referring to FIG. 2 it will be perceived that, in addition to theclearly established advantages of carrying out separate sulfonations ofthe two alkylates, the procedure of sulfonating the dimer alkylate whilethis alkylate is diluted with oil, and sulfonating the bottoms alkylateneat, followed by the addition of hexane after sulfonation, is thesuperior technique to be followed. Thus, in Examples 1 and 2, eachinvolving separate sulfonations of the two alkylates, with only thebottoms alkylate being sulfonated neat followed by hexane addition, bothruns produced sulfonic acids having substantially higher combiningweights than in the case of the separate sulfonation carried out inExample 3 where both alkylates were sulfonated neat. It will also benoted that the runs of Examples 1 and 2 yielded products with much loweracid ratios than the product made in Example 3. The yield is also betterin the two former runs. Only in the case of the color test does theprocedure of separately sulfonating each of the alkylates neat, followedby hexane addition, appear to give comparable results to those obtainedwhere the dimer alkylate is sulfonated in oil.

The sulfonic acid products produced by the runs described in Examples 1and 4 were overbased using a calcium alkoxide-carbonate complex inaccordance with the teachings of Hunt US. Pat. No. 3,150,088. Theviscosities of overbased calcium sulfonate dispersions produced by thistechnique from these two sulfonic acid products were compared. Theoverbased calcium sulfonate disper sion derived from the separatesulfonation procedure described in Example 1 had a base number of 290and had a viscosity (S.S.U. 210) of 409.3. As contrasted with this, theoverbased calcium sulfonate dispersion derived from the co-sulfonationprocedure set forth in Example 4 had a base number of 280 and had aviscosity of 879.3. Thus, a very significant improvement in viscositywas achieved through the use of the separate sulfonation technique, ascompared to the co-sulfonation procedure previously in use.

From the foregoing description of the invention, it will be perceivedthat the process of the invention provides a method by which mixedsulfonic acids derived from two alkylates of the general type describedcan be upgraded, and their utility as charge materials for the purposeof producing overbased sulfonate dispersions suitable for use aslubricating oils can be improved. Although certain preferred embodimentsof the invention have been herein described in order to provide examplessufficient to enable those skilled in the art to practice the invention,it will be understood that other materials and variations in thedescribed process conditions can be employed without departure from thebasic principles of the invention. Changes and innovations of this typeare therefore deemed to be circumscribed by the spirit and scope of theinvention except as the same may be necessarily limited by the appendedclaims or reasonable equivalents thereof.

What is claimed is:

1. The process of preparing a mixture of oil-soluble sulfonic acidscomprising:

sulfonating a first alkylate composition comprising at least weightpercent monoalkaryl compounds in which an aryl group is substituted byan alkyl substituent containing from about 20 to about 40 carbon atoms;

separately sulfonating a second alkylate containing from 5 weightpercent to about 35 weight percent diphenylalkanes, from about 5 weightpercent to about 50 weight percent alkylated tetralins, and from about25 weight percent to about weight percent di-n-alkylbenzenes, and havingan average molecular weight of from about 300 to about 500, the alkylsubstituents of said di-n-alkylbenzenes containing from about 8 to about18 carbon atoms;

separating sludge formed in the sulfonation of said first alkylate fromthe crude sulfonic acid produced upon sulfonation;

separating sludge formed in the sulfonation of said second alkylate fromthe crude sulfonic acid produced upon sulfonation;

combining the de-sludged crude sulfonic acid yielded from thesulfonation of said first alkylate with the desludged crude sulfonicacid yielded from the sulfonation of said second alkylate;

adding a hydrocarbon solvent diluent to the combined crude sulfonicacids; and

separating sludge from the hydrocarbon diluted-crude sulfonic acids.

2. The process defined in claim 1 wherein a light mineral oil diluent ismixed with said first alkylate prior to sulfonating said first alkylate.

3. The process defined in claim 1 wherein the sulfonations of said firstand second alkylates are carried out using oleum as the sulfonatingagent.

4. The process defined in claim 1 wherein said first alkylate is a dimeralkylate prepared by alkylating benzene with a dimer of a propylenetetramer, and wherein the substituents of the benzene after alkylationare highly branched alkyl groups containing from about 20 to about 40carbon atoms, said dimer alkylate having a molecular weight of fromabout 350 to about 600.

5. The process defined in claim 1 wherein said second alkylate boilsabove about C. at 5 mm. Hg and contains from about 40 weight percent toabout 75 weight percent di-n-alkylbenzenes in which the alkylsubstituents contain from 8 to 18 carbon atoms and are bonded to thebenzene group through a secondary carbon atom of the alkyl chain.

6. The process defined in claim 1 wherein said sludge is removed fromsaid crude sulfonic acids before combin ing said sulfonic acids bygravity settling said crude sulfonic acids for a period of from about 8hours to about 16 hours.

7. The process defined in claim 1 wherein, prior to separating sludgefrom crude alkylate formed in the sulfonation of said second alkylate,the reaction mixture produced upon sulfonation of said second alkylateis diluted with a parafiinic hydrocarbon solvent in an amount of fromabout 0.5 gram to about 3 grams of solvent per gram of the secondalkylate charged to the sulfonation reaction.

8. The process defined in claim 1 wherein said crude sulfonic acids arecombined in a 1:1 weight ratio of the sulfonic acids present in the twocrude sulfonic acids.

9. The process defined in claim 1 wherein the monoalkaryl compounds insaid first alkylate are alkyl substituted benzene compounds in which thealkyl substituents are substantially straight chain in character andcontain from about 20 to about 40 carbon atoms.

10. The process defined in claim 2 wherein said second alkylate issulfonated neat, and wherein, prior to separating sludge from the crudealkylate formed in the sulfonation of said second alkylate, the reactionmixture produced upon sulfonation of said second alkylate is dilutedwith a parafiinic hydrocarbon solvent in an amount of from about 0.5gram to about 3 grams of solvent per gram of the second alkylate chargedto the sulfonation reaction.

11. The process defined in claim 3 wherein during the sulfonation ofsaid first and second alkylates with oleum, the temperature of eachreaction mixture is maintained below about 80 C. during addition of theoleum to the alkylate.

12. The process defined in claim 2 wherein the hydrocarbon solventdiluent added to the combined crude sulfonic acids is a C -C paraflinichydrocarbon.

13. The process defined in claim 2 wherein said first alkylate is adimer alkylate prepared by alkylating benzene with a dimer of apropylene tetramer, and wherein the substituents of the benzene afteralkylation with said tetramer are highly branched alkyl groupscontaining from about 20 to about 40 carbon atoms, said dimer alkylatehaving a molecular weight of from about 350 to about 600.

14. The process defined in claim 2 wherein said mineral oil diluent ispale oil having a viscosity of about 100 SSU at 210 C.

15. The process defined in claim 2 wherein the sulfonation of said firstand second alkylates are carried out using oleum as the sulfonationagent and adding oleum to the alkylates while the temperature of eachalkylate is maintained below about 80 C.

16. The process defined in claim 13 wherein said second alkylate boilsabove about 160 C. at mm. Hg and contains from about 40 weight percentto about 75 weight percent di-n-alkylbenzenes in which the alkylsubstituents contain from about 8 to about 18 carbon atoms and arebonded to the benzene group through a secondary carbon atom of the alkylchain.

17. The process defined in claim 16 wherein the sulfonations of saidfirst and second alkylates are carried out using oleum as thesulfonating agent and adding oleum to the alkylates while thetemperature of each alkylate is maintained below about C.

18. The process defined in claim 17 wherein the hydrocarbon solventdiluent added to the combined crude sulfonic acids is normal hexane andis added in the ratio of from about 0.20 to about 1.5 volumes of hexaneper volume of the combined crude sulfonic acids.

19. The process defined in claim 18 wherein said crude sulfonic acid arecombined in a 1:1 weight ratio of the sulfonic acids present in the twocrude sulfonic acids.

20. The process defined in claim 16 wherein, prior to separating sludgefrom crude alkylate formed in the sulfonation of said second alkylate,the reaction mixture produced upon sulfonation of said second alkylateis diluted with a parafiinic hydrocarbon solvent in an amount of fromabout 0.5 gram to about 3 grams of hexane per gram of the secondalkylate charged to the sulfonation reaction.

References Cited UNITED STATES PATENTS 2,161,174 6/1939 Kyrides 252-353X 2,463,497 3/1949 Smith et al 252353 X 3,150,088 9/1964 Hunt et al.25232.7 R

RICHARD D. LOVERING, Primary Examiner US. Cl. X.R. 252--33

